LYMNZIDZ OF NORTH AMERICA. 103 
Horizon: Cache Valley beds, Humboldt Group, Pliocene Period, 
Locatity: Cache Valley, Cache County, Utah. 
Remarks: “This species is remarkable for having its surface 
ornamented by a very regular, vertical coste, quite strongly defined 
on its body-volution. This character will readily distinguish it from 
any other species, either recent or fossil, known to me, and, with its 
other characters, forbid its reference to any of the established sub- 
genera. In the possession of ribs, it agrees with Pleurolimnea, but it 
differs extremely in form from that type. I have therefore proposed 
for its reception a new subgenus under the name Polyrhytis. 
“T have seen but a single specimen of this shell, consisting of a 
well-defined mould, from which a gutta-percha cast has been taken, 
and from this the figures and description were prepared. The specific 
name is given in honor of Clarence King, Esq., the geologist-in-charge 
of the Survey of the Fortieth Parallel.” (Meek.) 
Lymnaea kingii and Lymnea tenuicosta were, until recently, unique 
among Lymneas, living or extinct, in the possession of strong longi- 
tudinal ribs. Meek (op. cit. 1876) erected the subgenus Polyrhytis 
for this species, giving the principal diagnostic character as “much like 
the last (Radix) in form, but bearing distinct regular, vertical coste.” 
In 1884,1 R. E. Call described a recent Lymnea (Lymnea ampla var. 
utahensis) from Lehi, Lake Utah, which is certainly congeneric with 
kingii and which may well be the descendant of the Pliocene fossil, 
having the shape of that species as well as the peculiar longitudinal 
cost. Call’s figures are not good and do not correctly represent the 
species. A good series of kingii is a desideratum in order that com- 
parison may be made with the recent species. 
It is thought by geologists? that the area of the Great Basin, in 
Utah, has formed in ages past a huge lake (Lake Shoshone), and it 
seems not at all unlikely that this unique Lymneid is the lineal ancestor 
of Call’s utahensis. 
Galba contracosta (Cooper). Plate XVII, figure 12. 
Limnea contracosta J. G. Cooper, Proc. Cal. Acad. Sci., ii, IV, p. 169, pl. 
14, fig. 12, 1894—Merrtam, Bull. Dept. Geol. Univ. Cal., 1, p. 363, 1896.— 
Lawson and Patacue, I. c., II, p. 391, 1902. 
Limnea contracosta J. G. Cooper, Bull. Cal. State Mining Bureau, IV, p. 
36, pl. 5, fig. 59, 1894. 
SHELL: “Form broadly ovate, whorls five, rapidly enlarging from 
an obtuse apex, and with convex outlines to the very large body whorl, 
tpn Us. Geol Surv., no. 11, p. 47. 
4King, Geol. 40th Parallel, Vol. I, p. 359-458. 
